1. Field of Invention
The invention relates to a scanner for scanning an object having undulations on a surface thereof, a lighting apparatus, and a scanning method.
2. Description of Related Art
A conventional scanner is known that scans an object having undulations on a surface thereof, for example, a double-page spread of a book. The scanner includes a scanning platform, a camera fixedly disposed opposed to the scanning platform, and a lighting apparatus that illuminates the scanning platform with light. The camera has a charged-couple device (CCD) line sensor, an optical system that forms an image of an object on a light receptive surface of the CCD line sensor by a scale-down of the image, and a reading mechanism that moves the CCD line sensor along an image plane.
When a page of a book is scanned, for example, as an object having undulations on a surface thereof, the book is opened to a desired page and placed on the scanning platform, and an image of the double-page spread is scanned by the camera. The camera scans an image through the CCD line sensor that is moved from a scanning start position at one end of a scanning area to a scanning end position at the other end to read in one line of the image. One line of the image data outputted from the CCD line sensor is stored in the memory of the camera, the CCD line sensor is moved for a specified pitch, and a next adjacent line of the image data outputted from the CCD line sensor is stored in memory. In this way, bitmapped image data is stored in memory of the camera, and transferred to an image storage medium of the scanner. If the camera is not provided with memory, the image data is directly stored in the image storage medium.
However, in the above-described scanner, the object to be scanned needs to be entirely illuminated with light of sufficient quantity under the same conditions from outside the scanning area of the camera, so as not to interfere with the scanning of the camera between the camera and the object. As a result, a plurality of lighting apparatuses are installed around the camera. If the camera is far away from the object to be scanned, lighting apparatuses producing a great amount of light are used. When a large-size object, for example, a relief that is a 2 meter square, is scanned, it is difficult to illuminate the entire surface of the object to be scanned with light under the same conditions. The same lighting conditions can be made with a plurality of lighting apparatuses in point of light quantity. However, when a plurality of lighting apparatuses are used, the illuminating direction can not be fixed with respect to every point of the surface of the object. This is because the light irradiating the surface of the object comes from not only a single lighting apparatuse but also other lighting apparatus having equal light quantity at one or more different locations. Therefore, shadows are not produced on the surface of the object in the same direction, and undulations on the surface of the object do not appropriately appear on the image obtained by scanning.
In particular, when the object to be scanned has uniform undulations in height on the surface like the above-described relief, the resultant scanned image of the object may not appear exactly life like to viewers. For example, when the object to be scanned is a relief or a cloth product made by covering a sponge or cotton pad having a fixed thickness with a cloth and stitching it thereon, a pattern with undulations of substantially the same height is formed on a surface thereof. If the lighting conditions are different at each point of the surface of the object to be scanned, shadows of the undulations do not favorably appear on the scanned image. Accurate relief images of a cloth product and relief are required for design quality as viewers tend to evaluate the quality of the image of the pattern showing the undulations on the surface as the quality of the relief or cloth product. As a result, if the quality of the image of the pattern is poor because of the difference in lighting conditions, viewers can not view the pattern correctly.
As described above, the larger an object to be scanned becomes, the worse the undulations of the object are reflected (portrayed) on the image. On the other hand, there is a method to produce an image without shadows of the undulation pattern by using a plurality of lighting apparatuses to increase the amount of light. However, the image without shadows of the undulation pattern appears different from the object scanned when observed in the natural light.